The present invention relates to a canister which is mainly used in a vehicle, such as an automobile. In particular, the present invention relates to a canister which can adsorb vaporized fuel generated in a fuel system.
In a vehicle, a canister is generally used in order to adsorb fuel vapor (which is called evaporation gas, purged gas or vaporized gas) generated in the fuel system.
For example, Japanese Laid-open Patent Publication Number 2000-64916 teaches a canister. As shown in FIG. 36, the canister includes a case 111. The case 111 has a first adsorbent layer 112a and a second adsorbent layer 112b that are separated from each other by a vertical dividing wall 115 disposed therein. Each of the adsorbent layer 112a and the adsorbent layer 112b is composed of granular adsorbent materials (not shown) that can adsorb fuel vapor.
The case 111 has a first space chamber 121a that is positioned on the first adsorbent layer 112a. The first space chamber 121a is communicated with an inlet port 122 and a purge port 123 that are formed in the case 111. The inlet port 122 communicates with a fuel tank (not shown), and the purge port 123 communicates with an intake pipe of an engine (not shown). The first adsorbent layer 112a and the first space chamber 121a are separated from each other by a gas permeable filter 113a. Conversely, the case 111 has a second space chamber 121b that is positioned on the second adsorbent layer 112b. The second space chamber 121b is communicated with an atmosphere port 124. The atmosphere port 124 is opened to an atmosphere. The second adsorbent layer 112b and the second space chamber 121b are separated from each other by a gas permeable filter 113b. 
The case 111 has a communication chamber 125 that is positioned under the first and second adsorbent layers 112a and 112b. The first and second adsorbent layers 112a and 112b and the communication chamber 125 are respectively separated from each other by gas permeable filters 114a and 114b. The filters 114a and 114b are respectively supported by grids 116a and 116b having ventilating holes 117. The grids 116a and 116b are respectively equipped with plate spring portions 118 and 120 that can press the grids 116a and 116b against the adsorbent layers 112a and 112b. The filters 113a, 113b, 114a and 114b are respectively formed from pad members that are made of a fibrous material or other such materials.
In the canister thus constructed, under a condition in which the engine is stopped, for example, when fuel is supplied to the engine, fuel vapor generated in the fuel tank flows into the first space chamber 121a through the inlet port 122. The fuel vapor flows through the first adsorbent layer 112a, the communication chamber 125 and the second adsorbent layer 112b with air, so as to be adsorbed by the adsorbent materials in the adsorbent layers 112a and 112b. Then, the air in which the fuel vapor is substantially removed is discharged into the atmosphere from the second space chamber 121b through the atmosphere port 124.
To the contrary, during operation of the engine, negative pressure generated in the intake pipe acts on an interior of the first space chamber 121a through the purge port 123. Due to the negative pressure, the fuel vapor that has been adsorbed to the adsorbent layers 112a and 112b is purged to the engine through the purge port 123. At this time, atmospheric air flows into the second space chamber 121b through the atmosphere port 124.